Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F9/00—Making metallic powder or suspensions thereof
  • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
  • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
  • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
  • B22F1/107—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material containing organic material comprising solvents, e.g. for slip casting
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/0466—Alloys based on noble metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/05—Metallic powder characterised by the size or surface area of the particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2301/00—Metallic composition of the powder or its coating
  • B22F2301/25—Noble metals, i.e. Ag Au, Ir, Os, Pd, Pt, Rh, Ru
  • B22F2301/255—Silver or gold

Definitions

• the present invention relates to a method for producing silver fine particles.
• silver exhibits high conductivity and oxidation resistance, it is widely used as a conductive material for wiring, electrodes, and the like.
• the silver fine particles used in the paste agent for forming them are required to have an appropriately small particle size, and particularly to have a uniform particle size. Further, the production of silver fine particles is required to have high productivity from the viewpoint of economy.
• Patent Document 1 As a method for producing silver fine particles for a paste agent for wiring and electrode formation, a wet reduction method (liquid phase reduction method) for reducing silver ions by a chemical method is the mainstream.
• a wet reduction method liquid phase reduction method
• a cationic surfactant is added to a reaction solution, and a raw material solution containing a silver compound is reduced using a reducing agent to reduce the silver fine particles.
• the method of manufacturing is described.
• the wet reduction method is performed in a batch manner as in Patent Document 1, it is difficult to obtain uniform silver fine particles because the reaction field becomes non-uniform due to the temperature gradient and the concentration gradient in the batch.
• a continuous reactor is used to flow a fluid containing a silver compound in one of the two flow paths and a fluid containing a reducing agent in the other.
• the two fluids are brought into contact with each other and mixed at the confluence of the two flow paths, and silver fine particles are precipitated by a wet reduction method to produce silver fine particles.
• the mixing of the two fluids is completed in a short time, and the reaction proceeds in a uniform state in the system, so that silver fine particles having a uniform shape and properties are produced.
• silver fine particles can be continuously produced, which is advantageous from the viewpoint of productivity.
• the silver mirror reaction is classified into a reduced non-catalytic type of the electroless plating technology, in which a silver salt solution and a reducing agent are mixed to form silver plating on the surface of the object to be plated.
• a silver salt solution and a reducing agent are mixed to form silver plating on the surface of the object to be plated.
• the reduction reaction in the silver mirror reaction proceeds not only on the surface of the object to be plated but also in the plating bath and on the wall surface of the plating bath container. Therefore, also in the methods for producing silver fine particles of Patent Documents 2 and 3, the reduction reaction proceeds not only in the reaction system but also in the merging portion and the inner wall of the flow path on the downstream side thereof, and the merging portion and the inner wall of the flow path Silver adheres to the surface to form a silver mirror.
• ammonia is added to silver nitrate to form an ammine complex, and ammoniacal silver nitrate is used as a raw material solution.
• ammoniacal silver nitrate due to the use of ammoniacal silver nitrate, the odor of ammonia is terrible and the working environment is very poor.
• ammoniacal silver nitrate has a problem that explosive fulminating silver is generated if it is left in contact with a reducing substance such as alcohol. Thus, the use of large amounts of ammonia should be avoided.
• Patent Document 4 describes a method for producing silver fine particles in the presence of sodium citrate.
• Citric acid can be a protective agent against silver, but since the coordinating power of citric acid with respect to silver ions is weaker than that of ammonia, it is not possible to sufficiently prevent the adhesion of silver in the continuous wet reduction method.
• Patent Document 5 and Patent Document 6 in a thin film fluid formed between at least two processing surfaces which are arranged so as to be close to each other and detachable from each other and at least one of them rotates relative to the other.
• a method for producing silver fine particles by a wet reduction method using a continuous forced thin film reactor that mixes reaction fluids is described.
• the self-discharging property of the forced thin film reactor can prevent the flow path from being blocked by the product, and uniform fine particles can be efficiently produced.
• Japanese Unexamined Patent Publication No. 61-243105 JP-A-2005-408236 Japanese Unexamined Patent Publication No. 2010-07793 Japanese Unexamined Patent Publication No. 2006-0456555 WO2009 / 0083390 WO2012 / 165000 Gazette Japanese Unexamined Patent Publication No. 2019-108610 Japanese Unexamined Patent Publication No. 2011-021252
• the problem to be solved by the present invention is to solve such a conventional problem, to have sufficient continuous productivity and quality uniformity in the wet reduction method using a continuous reactor, and to have a large amount of the problem. It is an object of the present invention to provide a method for producing silver fine particles, which does not have problems of deterioration of working environment and generation of explosive fulminating silver due to the use of ammonia.
• the present inventor has surprisingly found the above-mentioned plurality of silver fine particles in a method for producing silver fine particles in which silver fine particles are continuously precipitated by a redox reaction by mixing a plurality of fluids flowing from different flow paths. It was found that by adding an amino acid to at least one of the fluids, the adhesion of silver on the confluence and the inner wall of the flow path on the downstream side thereof is suppressed, and silver fine particles can be continuously and stably produced. , The present invention has been completed.
• the amino acid used in the present invention has two types of functional groups, an amino group and a carboxyl group, which can coordinate to a silver ion in the molecule.
• Amino acids are available in powder form, which is highly safe and easy to handle, so they can be effectively used as a substitute for ammonia.
• Patent Document 7 discloses a method for producing silver fine particles for a conductive paste, which uses a neutral or basic amino acid having 5 or more carbon atoms.
• the same production method is characterized in that by leaving amino acids in the generated silver fine particles, the silver fine particles can be sintered at a relatively low temperature to form a conductive film having a low volume resistivity.
• Amino acids are not used as a complexing agent for silver ions, but as impurities that remain in silver fine particles.
• a silver ammine complex prepared from silver nitrate and aqueous ammonia is used as a raw material, and ammonia is used as a complexing agent for silver ions. Therefore, it still has the problem of producing ammonia odor and explosive fulminating silver as in the prior art.
• Patent Document 8 discloses a method for precipitating silver fine particles in an aqueous solution containing an amino acid and an aliphatic hydroxy acid metal salt.
• the method is characterized by producing silver fine particles having a unique structure such as an X-shaped shape or a flower-shaped shape, and silver particles and amino acids for forming one component (aggregate) having a specific shape. Amino acids are used to produce nuclei consisting of.
• the reducing agent aqueous solution is added dropwise to the silver compound mixed aqueous solution without stirring, and the mixture is stirred at a low speed even after the addition is completed. Therefore, the method for producing silver fine particles of Patent Document 8 cannot be applied to a continuous wet reduction method in which a silver compound and a reducing agent are continuously and quantitatively mixed and reacted in a short time.
• the first aspect of the present invention is A method for producing silver fine particles, in which at least two fluids are introduced from different flow paths and mixed to continuously reduce silver ions contained in a silver compound to precipitate silver fine particles. Of the at least two fluids, one fluid contains the silver compound and the other fluid contains a reducing agent. A method for producing silver fine particles, which comprises containing an amino acid in at least one of the at least two fluids.
• a second aspect of the present invention is The method for producing silver fine particles according to the first aspect, wherein the production of silver mirrors is suppressed by the amino acids.
• a third aspect of the present invention is The method for producing silver fine particles according to the first or second aspect, wherein the fluid containing the silver compound contains the amino acids.
• a fourth aspect of the present invention is The method for producing silver fine particles according to any one of the first to third aspects, wherein 0.1 to 4 mol of the amino acid is used with respect to 1 mol of the silver ion.
• a fifth aspect of the present invention is The method for producing silver fine particles according to any one of the first to fourth aspects, wherein the concentration of the silver ions in the fluid containing the silver compound is 0.1 to 5% by mass.
• a sixth aspect of the present invention is The method for producing silver fine particles according to any one of the first to fifth aspects, wherein the dispersant is contained in at least one of the at least two fluids.
• a seventh aspect of the present invention is The method for producing silver fine particles according to any one of the first to sixth aspects, wherein the amino acid is glycine.
• the eighth aspect of the present invention is The first to seventh above, wherein the at least two fluids are mixed between at least two processing surfaces which are arranged so as to approach and separate from each other and at least one rotates relative to the other.
• a ninth aspect of the present invention is The method for producing silver fine particles according to any one of the first to eighth aspects described above, which does not use ammonia.
• the method for producing silver fine particles of the present invention silver does not adhere to the confluence of the continuous reactor and the inner wall of the flow path in the continuous wet reduction method using the continuous reactor. Therefore, with the passage of time, the environment of the confluence portion and the flow path does not change, the shape and properties of the silver fine particles to be produced can be controlled, and silver fine particles of a certain quality can be produced.
• the method for producing silver fine particles of the present invention has sufficient continuous productivity and quality uniformity in the wet reduction method using a continuous reactor, and the use of a large amount of ammonia deteriorates the working environment. Silver fine particles can be produced without the problem of producing explosive fulminating silver.
• At least two fluids are introduced from different flow paths and mixed to continuously reduce silver ions contained in a silver compound to precipitate silver fine particles.
• one of the at least two fluids contains the silver compound
• the other fluid contains a reducing agent
• at least one of the at least two fluids contains amino acids.
• Examples of the apparatus for producing silver fine particles used in the present invention include a continuous reactor having at least two flow paths and having a structure in which they are in contact with each other at the confluence.
• the structure of the confluence in the continuous reactor is not particularly limited.
• a flow path that merges at the merging portion for example, a Y-shaped pipeline, a T-shaped pipeline, a coaxial double pipeline, or the like can be used.
• a static mixer and an in-line mixer may be installed in the flow path on the downstream side of the merging portion for the purpose of promoting mixing, or a mechanism for mechanically stirring at the merging portion may be provided.
• various shear type, friction type, high pressure jet type, ultrasonic type and the like stirrers, or melters, emulsifiers, dispersers, crushers, homogenizers and the like can be used.
• these continuous reactors include Ultratarax (manufactured by IKA Japan Co., Ltd.), Homomixer (manufactured by Primix Corporation), Milder (manufactured by Taiheiyo Kiko Co., Ltd.), and Homomic Line Flow (manufactured by Primix Corporation).
• At least two kinds of fluids to be treated are contacted and mixed between at least two treatment surfaces in which at least one rotates relative to the other.
• Examples include forced thin film reactors that can. More specifically, the above two treatments are arranged so as to be close to each other and can be separated from each other, and at least one has a first treatment surface and a second treatment surface that rotate relative to the other. At least two types of fluids to be treated are introduced between the surfaces, and the pressure applied between the first surface and the second surface causes the first surface and the second surface to be treated.
• a separation force acting in the direction of separation is generated, and the pressure balance with the pressure in the direction of bringing the treatment surfaces closer to each other keeps the first treatment surface and the second treatment surface at a minute distance, and at least the above.
• a thin film fluid is formed by passing two types of fluids to be treated between the first surface to be treated and the second surface to be treated kept at a minute interval, and the fluids to be treated are formed in the thin film fluid. Examples include forced thin fluid reactors capable of contacting and mixing. Among them, the forced thin film reactor used in the present invention has a mechanism for promoting mixing by relatively moving the treatment surfaces at the mixing site of the fluid to be treated while maintaining a constant interval. Is preferable. Specifically, for example, the forced thin film type fluid processing apparatus shown in Japanese Patent Application Laid-Open No. 2010-189661 is preferably used.
• silver compound used in the present invention examples include monovalent, divalent or trivalent silver compounds dissolved in a solvent used in a fluid containing the silver compound, and preferably monovalent silver compound. Be done. Specific examples thereof include silver nitrate, silver fluoride, silver sulfate, silver phosphate and the like, and more preferably silver nitrate.
• the concentration of silver ions in the fluid containing the silver compound is preferably 0.1% by mass or more, for example, in order to increase productivity. Further, if the concentration of silver ions is too high, it becomes difficult to suppress the formation of a silver mirror. Therefore, for example, it is preferably 5% by mass or less.
• the concentration of silver ions is more preferably 0.5% by mass or more and 4.5% by mass or less, further preferably 1% by mass or more and 4% by mass or less, and even more preferably 1.5% by mass or more. 3% by mass or less can be mentioned.
• any reducing agent can be used as long as it can reduce silver ions contained in the silver compound and precipitate silver fine particles.
• Preferred reducing agents include, for example, ascorbic acid, ferrous sulfate, sulfite, alkanolamine, formic acid, hydroquinone, glucose, formalin, sodium boron hydride, hydrazine, hydrazine compounds (hydrazinium sulfate, hydrazine chloride, etc.) and the like. Be done. Among these, for example, hydrazine, hydrazine compounds and the like are more preferable.
• the amount of the reducing agent used is preferably 1 equivalent or more, more preferably 1 equivalent or more and 20 equivalents or less, still more preferably 1.5 equivalents or more, relative to silver ions in order to increase the reaction yield of the silver fine particles. 15 equivalents or less, and even more preferably 2 equivalents or more and 10 equivalents or less.
• electrons are transferred between compounds, and silver ions receive one electron and are reduced to silver.
• the number of electrons transferred from one molecule differs for each of the above reducing agents. For example, hydrazine provides 4 electrons in the reduction reaction.
• 1 equivalent or more with respect to silver ions means that hydrazine is 0.25 mol or more with respect to 1 mol of silver ions.
• a reducing agent having a weak reducing power it is preferably 2 equivalents or more, more preferably 2 equivalents or more and 50 equivalents or less, and further preferably 5 equivalents or more and 30 equivalents or less with respect to silver ions. Even more preferably, 10 equivalents or more and 20 equivalents or less can be mentioned.
• the concentration of the reducing agent in the fluid containing the reducing agent is preferably 1% by mass or more, for example, in order to increase productivity.
• concentration of the reducing agent is preferably 50% by mass or less, for example.
• concentration of the reducing agent is 2.5% by mass or more and 40% by mass or less, and more preferably 5% by mass or more and 25% by mass or less.
• the amino acid in the present invention has two types of functional groups, an amino group and a carboxyl group, which can be coordinated to silver ions in the molecule. Therefore, a mixture of various types of complexes in which an amino group, a carboxyl group, or the like is coordinated to a silver ion is formed.
• Amino acids stabilize silver ions by forming a mixture of silver ions and various types of complexes, reduce the reduction rate immediately after mixing the silver ions and the reducing agent, and confluence and flow paths of the continuous reactor. The formation of silver mirrors on the inner wall of the silver mirror is suppressed, and the adhesion of silver to the inner wall of the confluence and the flow path is suppressed.
• amino acid examples include ⁇ -amino acid, ⁇ -amino acid, derivatives thereof and the like, and can be appropriately selected depending on the physical properties such as solubility and pKa.
• Preferred amino acids include, for example, ⁇ -amino acids.
• Specific ⁇ -amino acids include, for example, glycine, arginine, phenylalanine, glutamic acid, valine, leucine, isoleucine, glutamine, aspartic acid, alanine, proline, cysteine, lysine (lysine), threonine (threonine), asparagine, serine, etc.
• Examples thereof include methionine, tyrosine, histidine, tryptophan, citrulin, ornithine and the like. More preferable ⁇ -amino acids include glycine, arginine, phenylalanine, glutamic acid and the like. Examples of ⁇ -amino acids and derivatives thereof include ⁇ -alanine, taurine, creatine and the like. Amino acids may be used alone or in combination of two or more. As for amino acids in which optical isomers are present, any of D-form, L-form, or a mixture thereof may be used.
• the amount of amino acid added is 5 mol or less per 1 mol of silver ion. Further, if the amount added is too small, silver ions become unstable and the formation of a silver mirror cannot be suppressed. Therefore, the amount is preferably 0.05 mol or more per mol of silver ions.
• a more preferable amount of the amino acid added is, for example, 0.1 mol or more and 4 mol or less, and more preferably 0.2 mol or more and 2 mol or less with respect to 1 mol of silver ion.
• amino acids are contained in at least one of at least two fluids introduced from different channels.
• the amino acid is contained in a fluid containing the silver compound.
• the silver ion forms a stable complex with the amino acid and can be reacted with the reducing agent in the state of the complex.
• the present invention also includes a mode in which a fluid containing a silver compound, a fluid containing a reducing agent, and a fluid containing an amino acid are introduced from separate flow paths and mixed.
• the solvent used in the fluid containing the silver compound or the reducing agent is a solvent capable of dissolving the silver compound or the reducing agent and which does not cause a problem in the reduction of silver ions. Anything can be used, if any.
• examples of such a solvent include water, a hydrophilic solvent, and a mixed solvent thereof, preferably water, and a mixed solvent of water and a hydrophilic solvent, and more preferably water.
• desalted water and specific examples thereof include ion-exchanged water, RO water (reverse osmosis water), pure water, and ultrapure water.
• hydrophilic solvent examples include alcohols such as methanol, ethanol and ethylene glycol, ketones such as acetone and methyl isobutyl ketone, sulfoxides such as dimethyl sulfoxide, amides such as dimethylformamide and dimethylacetamide, tetrahydrofuran, dioxane, dimethoxyethane and polyethylene.
• examples thereof include ethers such as glycol and carboxylic acids such as acetic acid.
• alcohols such as methanol, ethanol and ethylene glycol.
• water and a hydrophilic solvent A mixed solvent is preferred.
• the dispersant is not particularly limited and may be appropriately selected depending on the intended purpose.
• examples thereof include fatty acids and salts thereof, surfactants, organometallic compounds, chelating agents, polymer dispersants and the like.
• fatty acids and salts thereof include propionic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, arachidonic acid, ricinoleic acid and salts thereof.
• the surfactant examples include anionic surfactants such as alkyl sulfonates and alkylbenzene sulfonates, cationic surfactants such as alkylpyridinium salts and quaternary alkylammonium salts, polyoxyethylene alkyl ethers and the like. Nonionic surfactants, or mixtures thereof. Specific examples of the surfactant include Ajisper (registered trademark, manufactured by Ajinomoto Fine Techno Co., Ltd.), Hypermer (registered trademark, manufactured by Croda), Tween (registered trademark), Solplus (registered trademark, Lubrisol Japan Co., Ltd.).
• organometallic compound examples include acetylacetone tributoxyzinc, magnesium citrate, diethylzinc, dibutyltin oxide, dimethylzinc, tetra-n-butoxyzinc, triethylindium, triethylgallium, trimethylindium, trimethylgallium, monobutyltin oxide, and tetra.
• organometallic compound examples include isocyanatesilane, tetramethylsilane, tetramethoxysilane, monomethyltriisocyanatesilane, silane coupling agent, titanate-based coupling agent, and aluminum-based coupling agent.
• chelating agent examples include imidazole, oxadiazole, thiazole, selenazole, pyrazole, isoxazole, isothiazole, 1H-1,2,3-triazole, 2H-1,2,3-triazole, 1H-1,2,4.
• polymer dispersants can be used.
• amine-based polymer dispersants such as polyethyleneimine and polyvinylpyrrolidone
• hydrocarbon-based polymer dispersants having a carboxylic acid group in the molecule such as polyacrylic acid and carboxymethyl cellulose.
• examples thereof include a polymer dispersant, Poval (polyvinyl alcohol), and a polymer dispersant having a polar group such as a copolymer having a polyethyleneimine moiety and a polyethylene oxide moiety in one molecule.
• the polymer dispersant preferably has a molecular weight of 100,000 or less.
• Commercially available products can also be used, and examples of the commercially available products include Solsperse 20000, Solsperse 24000, Solsperse 26000, Solsperse 27000, Solsperse 28000, Solsperse 41000 (all manufactured by Nippon Lubrizol Co., Ltd.), and Disperbic 160.
• dispersants may be used alone or in combination of two or more.
• the dispersant can be included in at least one of at least two fluids introduced from different channels.
• the amount of the dispersant added it is preferable to use an amount of the dispersant that does not inhibit the coordination of amino acids to silver ions and does not adversely affect the effects of the present invention.
• the concentration of the dispersant in the fluid containing the dispersant is, for example, 0.0001% by mass or more and 1% by mass or less, preferably 0.0005% by mass or more and 0.5% by mass or less, more preferably. Is 0.001% by mass or more and 0.1% by mass or less.
• a pH adjuster may be added to adjust the difference in acidity derived from the raw material.
• general acids and bases can be used, and examples thereof include nitric acid and sodium hydroxide.
• reaction temperature of the reaction of introducing at least two fluids from different flow paths and mixing them to continuously reduce the silver ions contained in the silver compound is such that the solvent used is solidified. , Or a temperature that does not vaporize.
• Preferred reaction temperatures include, for example, 5 ° C. or higher and 80 ° C. or lower, more preferably 10 ° C. or higher and 60 ° C. or lower, further preferably 15 ° C. or higher and 50 ° C. or lower, and even more preferably 20 ° C.
• the temperature is 40 ° C. or lower.
• Example 1 250 parts of silver nitrate (manufactured by Kishida Chemical Co., Ltd.) as a silver compound, 111 parts of glycine (manufactured by Kanto Chemical Co., Ltd.) as an amino acid (1 mol per 1 mol of silver ion), and 60% nitrate as a pH adjuster (Kishida Chemical Co., Ltd.) 50 parts (manufactured by the company) was added to 9589 parts of ion-exchanged water and dissolved at 25 ° C. in an air atmosphere to prepare a silver compound aqueous solution (1).
• aqueous solution 150 parts of hydrazine / monohydrate (manufactured by Kanto Chemical Co., Ltd.) as a reducing agent, 5 parts of 10% oleic acid methanol solution in which oleic acid (manufactured by Kanto Chemical Co., Ltd.) is dissolved in methanol as a dispersant, and 845 parts of ion-exchanged water. And dissolved at 25 ° C. in an air atmosphere to prepare a reducing agent aqueous solution (1).
• a silver compound aqueous solution (1) is sent at 500 mL / min as the first fluid, and a reducing agent aqueous solution (1) is sent at 50 mL / min as the second fluid.
• the liquid was introduced between disks rotated at 500 rpm and mixed, and the discharged liquid was recovered from between the disks to obtain a slurry containing silver fine particles.
• the meanings of the first fluid and the second fluid are the same as those described in JP-A-2010-189661.
• the forced thin film reactor ULREA was continuously operated for 30 minutes to produce silver fine particles.
• the discharged liquid was divided and collected every 1 minute of operation time. After the operation was completed, when the processing surface of the used disc was checked, no silver adhesion was observed.
• the silver fine particles contained in the slurry were filtered under reduced pressure using a hard filter paper (opening 1 ⁇ m), and the residue after filtration was washed with ion-exchanged water three times, dried, and then crushed to obtain silver powder. ..
• the obtained silver powder was observed at a magnification of 10,000 times with a scanning electron microscope (trade name: JSM-7500F, manufactured by JEOL Ltd.) for each divided operation time.
• a scanning electron microscope (trade name: JSM-7500F, manufactured by JEOL Ltd.) for each divided operation time.
• Example 2 250 parts of silver nitrate (manufactured by Kishida Chemical Co., Ltd.) as a silver compound, 52 parts of L-arginine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as an amino acid (0.2 mol per 1 mol of silver ion), 60 as a pH adjuster 5 parts of% nitrate (manufactured by Kishida Chemical Industries, Ltd.) was added to 9693 parts of ion-exchanged water and dissolved at 25 ° C. in an air atmosphere to prepare an aqueous silver compound solution (2).
• L-arginine manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.
• 60 a pH adjuster 5 parts of% nitrate
• a silver compound aqueous solution (2) is sent at 500 mL / min as the first fluid, and a reducing agent aqueous solution (2) is sent at 50 mL / min as the second fluid.
• the liquid was introduced between disks rotated at 500 rpm and mixed, and the discharged liquid was recovered from between the disks to obtain a slurry containing silver fine particles.
• the forced thin film reactor ULREA was continuously operated for 30 minutes to produce silver fine particles.
• the discharged liquid was divided and collected every 1 minute of operation time. After the operation was completed, when the processing surface of the used disc was checked, no silver adhesion was observed.
• the silver fine particles contained in the slurry were filtered under reduced pressure using a hard filter paper (opening 1 ⁇ m), and the residue after filtration was washed with ion-exchanged water three times, dried, and then crushed to obtain silver powder. ..
• the particle size of the silver fine particles was about 0.6 ⁇ m, and no difference was observed in the particle size and shape from the start to the end of the operation. was confirmed.
• Example 3 250 parts of silver nitrate (manufactured by Kishida Chemical Co., Ltd.) as a silver compound, 243 parts of L-phenylalanine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as an amino acid (1 mol per 1 mol of silver ion), 60% nitrate as a pH adjuster 5 parts (manufactured by Kishida Chemical Industries, Ltd.) was added to 9502 parts of ion-exchanged water and dissolved at 25 ° C. in an air atmosphere to prepare an aqueous silver compound solution (3).
• silver nitrate manufactured by Kishida Chemical Co., Ltd.
• L-phenylalanine manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.
• 60% nitrate as a pH adjuster 5 parts
• a silver compound aqueous solution (3) is sent at 500 mL / min as the first fluid, and a reducing agent aqueous solution (3) is sent at 50 mL / min as the second fluid.
• the liquid was introduced between disks rotated at 500 rpm and mixed, and the discharged liquid was recovered from between the disks to obtain a slurry containing silver fine particles.
• the forced thin film reactor ULREA was continuously operated for 30 minutes to produce silver fine particles.
• the discharged liquid was divided and collected every 1 minute of operation time. When the processing surface of the used disc was checked, no silver adhesion was observed.
• the silver fine particles contained in the slurry were filtered under reduced pressure using a hard filter paper (opening 1 ⁇ m), and the residue after filtration was washed with ion-exchanged water three times, dried, and then crushed to obtain silver powder. ..
• the particle size of the silver fine particles was about 1.2 ⁇ m, and there was no difference in the particle size and shape from the start to the end of the operation. Was confirmed.
• Example 4 250 parts of silver nitrate (manufactured by Kishida Chemical Co., Ltd.) as a silver compound, 65 parts of L-glutamic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as an amino acid (0.3 mol per 1 mol of silver ion), 60 as a pH adjuster 5 parts of% glutamic acid (manufactured by Kishida Chemical Industries, Ltd.) was added to 9680 parts of ion-exchanged water and dissolved at 25 ° C. in an air atmosphere to prepare an aqueous silver compound solution (4). The same aqueous reducing agent solution as in Example 1 was prepared and used.
• a silver compound aqueous solution (4) is sent at 500 mL / min as the first fluid, and a reducing agent aqueous solution (1) is sent at 50 mL / min as the second fluid.
• the liquid was introduced between disks rotated at 500 rpm and mixed, and the discharged liquid was recovered from between the disks to obtain a slurry containing silver fine particles.
• the forced thin film reactor ULREA was continuously operated for 30 minutes to produce silver fine particles.
• the discharged liquid was divided and collected every 1 minute of operation time. When the processing surface of the used disc was checked, no silver adhesion was observed.
• the silver fine particles contained in the slurry were filtered under reduced pressure using a hard filter paper (opening 1 ⁇ m), and the residue after filtration was washed with ion-exchanged water three times, dried, and then crushed to obtain silver powder. ..
• the particle size of the silver fine particles was about 0.9 ⁇ m, and no difference was observed in the particle size and shape from the start to the end of the operation. was confirmed.
• ⁇ Comparative example 1 250 parts of silver nitrate (manufactured by Kishida Chemical Co., Ltd.) as a silver compound and 50 parts of 60% nitric acid (manufactured by Kishida Chemical Co., Ltd.) as a pH adjuster were added to 9700 parts of ion-exchanged water and dissolved at 25 ° C. in an air atmosphere.
• the silver compound aqueous solution (5) was used.
• the same aqueous reducing agent solution as in Example 1 was prepared and used.
• the silver compound aqueous solution (5) is sent as the first fluid at 500 mL / min, and the reducing agent aqueous solution (1) is sent as the second fluid at 50 mL / min.
• the liquid was introduced between disks rotated at 500 rpm and mixed, and the discharged liquid was recovered from between the disks to obtain a slurry containing silver fine particles.
• the forced thin film reactor ULREA was continuously operated for 3 minutes to produce silver fine particles.
• the discharged liquid was divided and collected every 1 minute of operation time. When the processing surface of the used disc was checked, silver adhesion was observed.
• the silver fine particles contained in the slurry were filtered under reduced pressure using a hard filter paper (opening 1 ⁇ m), and the residue after filtration was washed with ion-exchanged water three times, dried, and then crushed to obtain silver powder. ..
• a hard filter paper open 1 ⁇ m
• the residue after filtration was washed with ion-exchanged water three times, dried, and then crushed to obtain silver powder. ..
• coarse particles of 10 ⁇ m or more, fine particles of 0.1 ⁇ m or less, and particles having an irregular shape gradually became larger as time passed from the start of operation. It was confirmed that the particle size and shape changed significantly from the start of operation to the end of operation, such as an increase and intense adhesion (necking) between particles.
• Example 5 A silver compound aqueous solution (1) and a reducing agent aqueous solution (1) were prepared and used in the same manner as in Example 1.
• Silver fine particles were manufactured using a coaxial double conduit having an inner diameter of 8 mm (outer diameter 10 mm) and an inner diameter of 3 mm (outer diameter 4 mm) of the outer conduit.
• the silver compound aqueous solution (1) as the first fluid is 500 mL / min in the outer conduit of the coaxial double conduit, and the reducing agent aqueous solution (1) is 50 mL / min in the inner conduit of the coaxial double conduit as the second fluid.
• the liquids were sent in each of the above, and the fluids were contacted and mixed at the confluence portion where the coaxial double pipelines merged to form a single pipeline, and the discharged fluid was recovered from the single pipelines to obtain a slurry containing silver fine particles.
• Silver fine particles were continuously produced for 30 minutes under the above conditions.
• the discharged liquid was divided and collected every 1 minute of operation time. After the operation was completed, when the confluence of the coaxial double pipelines after use and the single pipelines on the downstream side were confirmed, no silver adhesion was observed.
• the silver fine particles contained in the slurry were filtered under reduced pressure using a hard filter paper (opening 1 ⁇ m), and the residue after filtration was washed with ion-exchanged water three times, dried, and then crushed to obtain silver powder. ..
• the particle size of the silver fine particles was about 0.9 ⁇ m, and no difference was observed in the particle size and shape from the start to the end of the operation. was confirmed.
• Silver fine particles were manufactured using a coaxial double conduit having an inner diameter of 8 mm (outer diameter 10 mm) and an inner diameter of 3 mm (outer diameter 4 mm) of the outer conduit.
• the silver compound aqueous solution (5) as the first fluid is 500 mL / min in the outer conduit of the coaxial double pipeline, and the reducing agent aqueous solution (1) is 50 mL / min in the inner conduit of the coaxial double pipeline as the second fluid.
• the fluids were sent in each of the above, contacted and mixed at the confluence where the coaxial double pipelines merged to form a single pipeline, and the discharged fluid was recovered from the single pipeline to obtain a slurry containing silver fine particles.
• Silver fine particles were continuously produced for 10 minutes under the above conditions.
• the discharged liquid was divided and collected every 1 minute of operation time. After the operation was completed, when the confluence of the coaxial double pipelines after use and the single pipelines on the downstream side were confirmed, silver adhesion was observed.
• the silver fine particles contained in the slurry were filtered under reduced pressure using a hard filter paper (opening 1 ⁇ m), and the residue after filtration was washed with ion-exchanged water three times, dried, and then crushed to obtain silver powder. ..
• a hard filter paper open 1 ⁇ m
• the residue after filtration was washed with ion-exchanged water three times, dried, and then crushed to obtain silver powder. ..
• coarse particles of 10 ⁇ m or more, fine particles of 0.1 ⁇ m or less, and particles having an irregular shape gradually became larger as time passed from the start of operation. It was confirmed that the particle size and shape changed significantly from the start of operation to the end of operation, such as an increase and intense adhesion (necking) between particles.
• Table 1 summarizes the added amino acids of Examples 1 to 5 and Comparative Examples 1 and 2, the operation time, the presence or absence of adhesion, and the change over time in the particle size and shape of the silver fine particles.
• the shape and properties of the silver fine particles to be produced can be controlled without changing the environment of the confluence and the flow path with the passage of time, and silver fine particles of a certain quality can be produced. .. Therefore, according to the method for producing silver fine particles of the present invention, in the wet reduction method using a continuous reactor, silver fine particles have sufficient continuous productivity and quality uniformity without using ammonia, which deteriorates the working environment. Can be manufactured.

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• 2019
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